1. Field of the Invention
This invention relates to the repair of a ship's hull, and, more particularly, to a system for temporarily patching a leak in a ship's hull to prevent the ingress of sea water into the ship and the egress of a liquid cargo such as oil from the ship.
2. Description of the Prior Art
Various systems have been developed for temporarily sealing holes or leaks in ship's hulls either to prevent the ingress of sea water into the ship or to prevent the egress of the ship's cargo, notably oil, thus leading to sea water contamination, or to seal against both influx and outflow through the leak. The objective in these systems is to temporarily contain the leak until permanent repairs can be accomplished so as to prevent the sinking of the ship by inflow and outflow where more serious damage occurs. With less drastic leaks, damage to the cargo by influx of sea water is of paramount importance, and in the case of tankers, damage to the environment by outflow is to be eliminated or minimized.
Various types of inflatable bladders or concentric inflatable chambers have been used, anchored to the ship by rigging or securing lines. Sometimes a foam blanket is interposed between the bladder or concentric inflatable conduits to be compressed inward into the hole or rupture to effect the seal. Various frame structures have been used to increase the mechanical advantage or sealing pressure around the peripheries of the leak to contain it. Sometimes the leaking oil is drawn off between alternate sealing and collecting chambers.
The usefulness of magnets has been recognized as a means of holding anchoring lines or the patch itself to the steel hull. Likewise, the increased usefulness of electromagnets was recognized in the process of securing the patch device so that the patch could be positioned over the leak by divers or positioning gear, and once positioned, the current could be applied to the electromagnet to effect the attraction and holding of the patch or lines to the steel hull.
In containing larger leaks, combinations of inflatable elements, canvas type curtains, sustaining weights and spaced magnets have been used to form a type of cofferdam confining the leak area so that leaking oil may be drawn off before it contaminates the sea water.
With smaller leaks, electromagnets have been arranged in a spaced circular pattern around a patch material to temporarily hold the patch against the hull until a marine glue or adhesive sets up. Somewhat larger leaks have been contained with circular patterns of spaced magnets used with a canvas structure and reinforcing bars along with pressure tubes for sealing or discharge tubes to draw sea water or leaking oil away. Permanent magnets have also been used around three sides of a rectangular periphery to hold a water proof curtain against the ship hull to a point above the water line.